The present invention relates to application-specific integrated circuits (ASICs) and, more particularly, to an ASIC that facilitates digital rights management for copyrighted material.
The term “digital rights management” (DRM) encompasses, generally, the secure distribution, promotion and sale of proprietary data such as, but not limited to, audio and video digital content. DRM imposes certain responsibilities on the content owner and on the content consumer. The content owner must create the digital work, protect the digital work by encrypting it, and distribute the encrypted digital work. The consumer downloads the encrypted digital work to his/her platform and pays for a license to decrypt and use the encrypted digital work.
Among the ways in which DRM can be implemented on a remote platform such as a mobile telephone, a personal computer, a set-top box or an audio player, are the following:
1. Software protection only: a software module integrated in the operating system of the platform controls authentication and data decryption. The main drawback of this solution is the lack of a secured element to store the secret keys used for authentication and decryption and for performing the authentication and decryption. Another drawback of this solution is that the cryptographic computations are not done in a secure, encapsulated environment. A hacker can copy and duplicate the decrypted data simply by probing the platform bus.
2. Secure system: the entire DRM process is performed by one or more hardware-protected (co)processor(s). This solution provides a higher level of security.
FIG. 1 is a high-level partial schematic illustration of a DRM system that includes a server 48 for storing and dispensing encrypted digital audio or video data and a remote platform 10. In the specific embodiment of a DRM platform that is illustrated in FIG. 1, server 48 is located at a base station 46 of a cellular telephony network and remote platform 10 is a mobile telephone that includes a transceiver 12 and an antenna 14 for communicating with base station 46. The overall operation of mobile telephone 10 is controlled by a microprocessor-based controller 16 in conjunction with a hardware-protected cryptographic coprocessor 18. Controller 16 typically includes two microprocessors: one microprocessor for controlling transceiver 12 and the other microprocessor for controlling the other components of mobile telephone 10. Cryptographic coprocessor 18 is represented in FIG. 1 as a subscriber identity module (SIM) such as is used in mobile telephony systems under the GSM standard. Using transceiver 12 and antenna 14, controller 16 transmits to server 48 at base station 46 a request (including user identification and payment instructions) to download encrypted digital audio or video data. In response, server 48 transmits the encrypted digital audio data back to mobile telephone 10. Controller 16 uses antenna 14 and transceiver 12 to receive the encrypted digital data, and then stores the encrypted digital data in a non-volatile memory 22 that could be, for example, a magnetic hard disk, a flash memory or an EEPROM. With regard to form factor, non-volatile memory 22 could be an on-board chip, or alternatively a removable device such as a MMC card or a SD card. When the user of mobile telephone 10 wishes to play the data, controller 16 retrieves the encrypted digital data from memory 22. The encrypted digital data then are decrypted by SIM 18, and the decrypted digital data are sent to a player 20. For example, if the downloaded data are audio data, player 20 could be an MP3 player. Player 20 then transforms the decrypted digital audio data to analog signals, optionally amplifies the analog signals, and sends the analog signals to a speaker 24 that transforms the audio signals into audible sound.
Components 12, 16, 18, 20 and 22 typically are realized as separate integrated circuits that communicate with each other via one or more common buses 26.
It is commonly recognized that the most secure form of DRM relies on a public key infrastructure. Preferably, the authentication of remote platform 10 to the base station is effected using an asymmetrical algorithm such as RSA, and the encryption and decryption of the digital audio data is effected using a symmetrical algorithm such as DES. The DES encryption keys that remote platform 10 needs to decrypt the encrypted digital data are encrypted using the asymmetrical algorithm prior to being sent to remote platform 10 by the base station.
In the embodiment of remote platform 10 that is illustrated in FIG. 1, SIM 18 serves as the hardware-protected DRM coprocessor. SIM 18 authenticates remote platform 10 to the base station via controller 16 and transceiver 12 and decrypts the DES keys. Controller 16 uses the decrypted DES keys to decrypt the encrypted digital data stored in memory 22 and then sends the decrypted digital data to player 20. All the keys needed to implement the authentication of remote platform 10 and the cryptographic functionality of remote platform 10 are stored in SIM 18. The main drawback of this embodiment is that controller 16 sends the digital data to player 20 in clear format, so that a hacker could copy and duplicate the digital data simply by probing bus 26.
Two alternate embodiments of remote platform 10 are known, in which a separate cryptographic coprocessor such as SIM 18 is not used to implement any of the cryptographic functionality.
In the first alternate embodiment of remote platform 10, controller 16 is the hardware-protected DRM processor, and all the cryptographic functionality is handled by controller 16. Controller 16 authenticates remote platform 10 to the base station, decrypts the encrypted digital data stored in memory 22, and sends the decrypted digital data to player 20. All the keys needed to implement the cryptographic functionality are stored in controller 16. The main drawback of this alternate embodiment is the same as the main drawback of the embodiment of FIG. 1: controller 16 sends the digital data to player 20 in clear format, so that a hacker could copy and duplicate the digital audio data simply by probing bus 26.
In the second alternate embodiment of remote platform 10, the cryptographic functionality is distributed between controller 16 and player 20, so that both controller 16 and player 20 serve as hardware-protected DRM processors. Controller 16 authenticates remote platform 10 to the base station and sends the encrypted digital data to player 20. Player 20 decrypts the encrypted digital data. The keys needed for authentication are stored in controller 16. The keys needed for decryption are stored in player 20. The main drawback of this alternate embodiment is the extra expense of two components with cryptographic capabilities.
An additional drawback of the two alternative embodiments, as compared to the embodiment of FIG. 1, is that controller 16 and player 20 of FIG. 1 are pure logic integrated circuits. Controller 16 of the two alternative embodiments, and player 20 of the second alternative embodiment, must also include their own read/write nonvolatile memories, so that the secret cryptographic keys can be replaced as necessary. Integrating a non-volatile memory in an otherwise pure logic integrated circuit may raise the cost of the integrated circuit substantially.
There is thus a widely recognized need for, and it would be highly advantageous to have, a hardware-protected DRM ASIC for remote platforms that would overcome the disadvantages of presently known systems as described above.